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Phase 3 - Kingdom Protista InformationIntroduction to Kingdom Protista

The Kingdom Protista includes an incredible diversity of different types of

organisms, including algae, protozoans, and slime molds. No one even knows how

many species there are, though estimates range between 6,!!! to "!!,!!!.

#ll protists are eukaryotes, comple$ cells with nuclear membranes and organelles

like mitochondria and chloroplasts. They can be either unicellular or

multicellular, and in this group we find the first inkling of what is to come in

evolutionary history, the union of eukaryotic cells into a colonial organism, where

various cell types perform certain tasks, communicate with one another, and

together function like a multicellular organism.

%ome protists are autotrophs, a photosynthetic group of phyla referred to as

the algae. #utotrophs manufacture their own energy by photosynthesis or

chemosynthesis. #lgae use various combinations of the ma&or chlorophyll

pigments, chlorophyll a, b, and c, mi$ed with a wide array of other pigments that

give some of them very distinctive colors.

%ome protists are heterotrophs,a group of phyla called the protozoa.

'eterotrophs get their energy by consuming other organisms. Protists

reproduce ase$ually by binary fission, and a few species are capable of se$ual

reproduction. (any have very comple$ life cycles.

Protists are so small that they do not need any special organs to e$change gases

or e$crete wastes. They rely on simple diffusion, the passive movement of

materials from an area of high concentration to an area of low concentration, to

move gases and waste materials in and out of the cell. )iffusion results from the

random motion of molecules *black and white marble analogy+. This is a two

edged sword. They dont need to invest energy in comple$ respiratory or

e$cretory tissue. -n the other hand, diffusion only works if youre really small,

so most protists are limited to being small single cells. Their small size is also

due to the inability of cilia or flagella to provide enough energy to move a large

cell through the water.

Protists eat by phagocytosis they engulf their food in their cell membrane, and

pinch off a section of membrane to form a hollow space inside the cell. This

hollow space, now enclosed by membranes, is called a vacuole. acuoles are handy

little structures. Protists also use them to store water, enzymes, and waste

products. Paramecium and many other protists have a comple$ type called a

contractile vacuole, which drains the cell of waste products and s/uirts them

outside the cell.

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#ll protists are a/uatic. (any protists can move through the water by means of

flagella, or cilia, or pseudopodia *0 false feet+. 1ilia and flagella are tiny movable

hairs. (otile cells usually have one or two long flagella, or numerous shorter cilia.

The internal structure of cilia and flagella is basically the same. #ll of the

characteristics that this group shares are primitive traits, a perilous thing tobase any classification on, because convergent evolution may be responsible for

these superficial similarities. %o the concept of the Kingdom Protista has been

&ustly criticized as a ta$onomic grab bagfor a whole bunch of primitive

organisms only distantly related to one another.

Protists are mainly defined by what they are not they are not bacteria or

fungi, they are not plants or animals. Protists gave rise to all other plants and

animals. 2ut where did protists themselves come from3 The earliest protists we

can recognize in the fossil record date back to about 4 billion, "!! million yearsago. 5e do not know how the various groups of protists are related to one

another. 5e assume they arose from certain groups of bacteria, but which

groups and when are still investigating. )ifferent phyla of protists are so unlike

one another, many probably evolved independently from completely different

groups of bacteria. ynn (argulis recognizes nearly ! different phyla of

protists, or Protoctista, as this kingdom is sometimes called. 5e will take a more

conservative approach, and focus on nine important phyla of protists.

Taxonomy

Kingdom Protista *Protoctista+

Protozoa 0 heterotrophic protists7

Phylum 1iliophora *Paramecium, 2lepharisma+

Phylum %arcodina *#moeba, radiolarians+

Phylum %porozoa *Plasmodium malaria+

#lgae 0 autotrophic protists

Phylum Phaeophyta brown algae *8ucus+

Phylum 9hodophyta red algae *Polysiphonia+

Phylum 1hrysophyta diatoms

Phylum :uglenophyta *:uglena+

Phylum Pyrrophyta dinoflagellates *1eratium+

http://pangea.tec.selu.edu/~cmcnabb/etec645/protist2.html#Phylum%20Ciliophorahttp://pangea.tec.selu.edu/~cmcnabb/etec645/protist2.html#Phylum%20Sarcodinahttp://pangea.tec.selu.edu/~cmcnabb/etec645/protist2.html#Phylum%20Sporozoahttp://pangea.tec.selu.edu/~cmcnabb/etec645/protist2.html#Phylum%20Phaeophytahttp://pangea.tec.selu.edu/~cmcnabb/etec645/protist2.html#Phylum%20Rhodophytahttp://pangea.tec.selu.edu/~cmcnabb/etec645/protist2.html#Phylum%20Bacillariophytahttp://pangea.tec.selu.edu/~cmcnabb/etec645/protist2.html#Phylum%20Euglenophytahttp://pangea.tec.selu.edu/~cmcnabb/etec645/protist2.html#Phylum%20Pyrrophythttp://pangea.tec.selu.edu/~cmcnabb/etec645/protist2.html#Phylum%20Ciliophorahttp://pangea.tec.selu.edu/~cmcnabb/etec645/protist2.html#Phylum%20Sarcodinahttp://pangea.tec.selu.edu/~cmcnabb/etec645/protist2.html#Phylum%20Sporozoahttp://pangea.tec.selu.edu/~cmcnabb/etec645/protist2.html#Phylum%20Phaeophytahttp://pangea.tec.selu.edu/~cmcnabb/etec645/protist2.html#Phylum%20Rhodophytahttp://pangea.tec.selu.edu/~cmcnabb/etec645/protist2.html#Phylum%20Bacillariophytahttp://pangea.tec.selu.edu/~cmcnabb/etec645/protist2.html#Phylum%20Euglenophytahttp://pangea.tec.selu.edu/~cmcnabb/etec645/protist2.html#Phylum%20Pyrrophyt

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Phylum 1hlorophyta green algae *%pirogyra, olvo$, 1hlamydomonas+

Characteristics of PhylaThe protozoa:

Phylum 1iliophora *;,!!! sp.,+ 2lepharisma, Paramecium

These ciliates move by means of numerous small cilia. They are comple$

little critters, with lots of organelles and specialized structures. (any of

them, like Paramecium, even have little to$ic threads or darts that they

can discharge to defend themselves. Typical ciliates you may see in lab

include Paramecium and 2lepharisma.

Phylum %arcodina *over

These ciliates have a most unusual way of getting about. They e$tend part

their body in a certain direction, forming a pseudopod or false foot, and

then flow into that e$tension *cytoplasmic streaming+. (any forms have a

tiny shell made from organic or inorganic material. They eat other

protozoans, algae, and even tiny critters like rotifers. #moeba is a typical

member of this phylum. (any sarcodines are parasites, such as the

species :ntamoeba histolytica, which causes amoebic dysentery. 4! million

#mericans are infected at any one time with some form of parasitic

amoeba, and up to half of the population in tropical countries. %omewhatmore unusual sarcodines are the 8oraminiferans. These foramscan

have fantastically sculptured shells, with prominent spines. They e$tend

cytoplasmicpodiaout along these spines, which function in feeding

and in swimming. 8orams are so abundant in the fossil record, and have

such distinctive shapes, that they are widely used by geologists as

markers to identify different layers of rock. The famous white cliffs of

)over are made up of billions of foraminiferan shells.

Phylum %porozoa *n more general terms, spores are haploid

reproductive cells that can develop directly into adults.

The algae:

Phylum Phaeophyta *4,!! species, fr. ?reek phaios 0 brown+ 8ucus

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This phylum contains the brown algae, %argassum, and the various species

of kelp. 2rown algae are the largest protists, and are nearly all marine.

Kelp blades can stretch up to 4!! meters long. 2rown algae have thin

blades with a central midrib or stipe. ike all algae, their blades are thin

because they lack the comple$ conductive tissues of green plants*phloem+, and must rely on simple diffusion, though some kelp have

phloemlike conducting cells in the midrib. Kelp form the basis of entire

ecosystems off the coast of 1alifornia and in other cool waters. >n the

%argasso %ea, the #tlantic -cean northeast of the 1aribbean

>slands, the brown algae %argassum forms huge floating mats, said in

older days to trap entire ships, holding them tight until the crew met a

watery grave.

Phylum 9hodophyta *fr. ?reek rhodos 0 red, @,!!! sp.+ Polysiphonia

ike brown algae, the red algae also contain comple$ forms, mostly marine,

with elaborate life cycles. 1hloroplasts in this group show pigments very

similar to those found in cyanobacteria, and ancient red algae may have

engulfed these cyanobacteria as endosymbionts. 9ed algae have many

important commercial applications, such as the agar used for culture

plates. >ts cell walls contain carrageenan, a polysaccharide used in the

manufacture of ice cream, paint, and cosmetics.

Phylum 2acillariophyta *44,!! sp., many more fossil sp., fr. atin bacillus 0 little

stick+ diatoms

)iatoms have a goldenbrown pigment. %ome books still place them with

the 1hrysophyta, the goldenbrown algae, but they are now recognized as

an entirely separate group. )iatoms have odd little shells made of organic

compounds impregnated with silica. The shells fit over the top of one

another like a little bo$. )iatoms usually reform the lower shell after they

divide This means they become smaller and smaller, and when they become

too small they leave their shells and fuse through se$ual reproduction into

a larger size and start over again. They are one of the most importantorganisms in both freshwater and marine food chains. )iatoms are so

abundant that the photosynthesis of diatoms accounts for a large

percentage of the o$ygen added to the atmosphere each year from

natural sources. Their dead shells form huge deposits, that are mined for

commercial uses. )iatom shells are sold as diatomacious earth, and used in

abrasives, talcs, and chalk. )iatoms are so numerous that their shells

form thick deposits all over the world. # single /uarry in ompoc,

1alifornia, yields over "A!,!!! metric tons per year. -ne bed in the %anta

(onica 1a. oil fields is over =!! meters thickB arious species of diatomsare also widely used as indicator species of clean or polluted water.

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Phylum :uglenophyta *;!! sp.+ :uglena

>s it a plant, or is it an animal3 >t moves around like an animal, and

sometimes eats particles of food, but a third of them are also

photosynthetic, a nice bright green pigment like a green algae *which itused to be called+. This organism may actually have resulted from

endosymbiosis, in which an ancestral form engulfed a green algal cell.

Phylum Pyrrophyta *

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of sacrifice that tells us an invisible line has been crossed. %ingle celled

bacteria and protists are immortal. They can go on dividing in two forever,

and so never truly die. 2ut in the Kingdom Protista, we see the beginnings

of specialization among groups of cells, specialization which entails the

death of certain cells so that other cells can survive. #s olvo$ remindsus, the price of comple$ multicellularity is death.

Things to RememberProtists are so small that they do not need any special organs to e$change gases

or e$crete wastes. They rely on simple diffusion, the passive movement of

materials from an area of high concentration to an area of low concentration, to

move gases and waste materials in and out of the cell.

Protists eat by phagocytosis they engulf their food in their cell membrane, and

pinch off a section of membrane to form a hollow space inside the cell. Thishollow space, now enclosed by membranes, is called a vacuole.

conomic! cological! and "olutionary Importance #lgae and protozoa are important prey in food chains. :ven humans eat

algae.

(any protozoans are important disease causing organisms *malaria,

to$oplasmoisis, amoebic dysentery+

)inoflagellates cause billions of dollars in damage to the seafood industry,

and are important symbionts in corals and other marine animals.

#n e$tract of red algae is used to make paint, cosmetics, and ice cream.

Protozoans gave rise to all higher forms of animal life.

?reen algae gave rise to all higher plant life.

2acteria first mastered the fine art of photosynthesis. 1yanobacteria

established the o$ygen atmosphere we breathe today. 2ut diatoms are

mainly responsible for current o$ygen input from photosynthesis.